Green renovations may be remodelers’ key to success in this work-slashed era--and knowing how to properly build a tight envelope, choose the most energy-efficient windows for the budget, and install connections for solar hookups, will be a must in the future, according to sustainable retrofit expert David Johnston during a Webinar for GreenExpo365.com.
Nevertheless, homes remodeled to meet Energy Star requirements are a mere start, said Johnston, who has worked in the construction industry for more than 30 years and has authored several books on green building, including “Toward a Zero Energy Home.”
“Our future is zero-energy,” he predicted, estimating that California will be the first to make zero-energy buildings code in the next 10 years.
Johnston recommended renovating homes to 50% above energy code standards and offered a few tips to help remodelers get there:
Focus on the envelope. When people think green, they often think solar; but the remodeler should channel the client’s money first into the shell of the house. The first priority should be insulating the exterior, choosing the most energy-efficient windows the budget can afford, and properly waterproofing to prevent mold from infecting the airtight home.
Insulate everything. To maximize the home’s energy-saving potential, get to know your insulation options. “The key is being clever and getting as much insulation into the wall as we can,” Johnston said. “Everything helps.”
And not just behind the walls--where the walls intersect the ceiling, around recessed cans, and the knee wall in the attic. Every gap is a potential cold spot and needs to be packed with insulation, he advised. Ceilings should typically have more insulation than walls.
In addition, pros should wrap the foundation exterior with 2-inch closed-cell rigid foam from the top to the footing. If there is no space on the exterior, insulate the inside. Likewise, insulate and seal crawlspaces if there is no basement, covering the floor and walls with waterproof membrane and overlapping it at every seam.
Don’t neglect the air spaces above recessed lights; build a box around them or cap with noncombustible installation (but Johnston advised to first replace them with high-efficiency LED lighting).
Also, insulate the pipes and wrap the water heater. Finally, properly weather-strip and caulk everything.
Install highly efficient windows. Window R-values have started to approach the R-values of well-insulated walls, with some fixed-glass units having a thermal resistance as high as R-14 or a U-value of 0.07. Johnston particularly likes products with foam-filled fiberglass frames and Heat Mirror low-E film.
Protect against mold. While securing for air leaks, watch out for moisture ingress. Rainscreens are the secret to siding longevity, giving moisture a way to drain down. With the stakes so high, Johnston is extreme in his exhortation: “I don’t want to just reduce mold, I need to remove it completely.”
Use the smallest HVAC system possible. “We want to be investing our client’s money into the envelope of the building,” said Johnston. “Mechanical systems are the last stop.” A well-designed HVAC system will meet the home’s reduced heating and cooling requirements and no more.
To improve efficiency and air quality, install sealed-combustion furnaces, boilers, and water heaters but make sure forced-air systems have positive pressure and do not suck bad air or carbon monoxide into the home.
Keep ducts inside the envelope as much as possible and insulate everything. Leaky ducts cost energy, can cause back drafting from fuel-burning appliances, and allow moist mold-producing air into unconditioned spaces.
Furthermore, replace fiberglass filters with one that has a higher MERV rating; a pleated media filter is the most cost-effective option.
Employ night flushing. A whole-house fan that draws cool night air in through open windows uses less energy than the air conditioning unit, and with a tight envelope, the house will stay cool all morning after the windows are shut tight again.
Plan for solar. To get to zero energy, installing photovoltaic panels is a requirement, the presenter said. But if the client cannot afford solar panels or a solar water heater now, install the hookups while the walls are open. They will thank you later.
Don’t forget energy audits. As important as it is to get a blower door test, infrared images, a duct blaster test, temperature gauge, and flow hood test before the job starts, it’s just as important at the end to see what was missed.
Johnston concluded: “It’s not that hard [to get to net zero]; builders are doing it for less than 10% incremental cost.” While it takes some research, some practice, and a little green enthusiasm, “the second or third time you do it, you’ve pretty much got the system down.”
Evelyn Royer is assistant editor for Building Products magazine.